Don't scan for devices when resuming and there is no lock screen.
Don't scan for devices when resuming and there is no lock screen.

BUG=549529

Review URL: https://codereview.chromium.org/1425533007

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#357528}

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